When the detaching solution 7 penetrate all over the adhesive layer 4, the wafer 2 and the support plate 1 can be separated more reliably.As the detaching solution, alcohol (especially low molecular weight alcohol such as ethanol or methanol), ketone, or the mixture of alcohol and ketone is used.Next, if the adhesion level between the wafer 2 and the support plate 1 becomes sufficiently low, the s